Having arrived at the station in September, replacing Graham Dene, Fox attracted 804,000 listeners this quarter, the highest for Magic's breakfast slot since the first quarter of 2005.
Magic has achieved overall leadership in the London market, and is the third place in the important breakfast show battle with the veteran presenter and former Capital Radio drivetime DJ is on hot on the heels of Capital's Vaughan and Heart's Theakston.
Vaughan remains top dog in London with 963,000 listeners, having lost 24,000 from last quarter, while Theakston had 855,000 listeners this quarter, which is 63,000 less than last quarter.
Kiss FM's Bam Bam pulled in 658,000 listeners in his last Rajars, compared with 683,000 in the previous quarter. Bam Bam left Kiss last month after seven years and the station has put Robin Banks in the slot on a temporary basis.
The long-anticipated arrival of Christian O'Connell at Virgin Radio in January failed to boost Virgin Radio's London breakfast audience. The show attracted 622,000 listeners, down in comparision to the 628,000 former breakfsat presenters Pete and Geoff attracted in the previous quarter.
LBC's Nick Ferrari, who won a Sony award for best breakfast show this week, enjoyed further success. He increased his show's reach from 361,000 to 402,000.
Also on the up is Xfm, where Lauren Laverne and Shaun Keaveny have dispelled worries over how the station would cope after its former star O'Connell quit in October last year. Laverne, with Keaveny on Fridays, got 340,000 listeners, up from 275,000 in the previous quarter.
Nationally, Terry Wogan on BBC Radio 2 remains the most-listened to DJ, with 7.76m tuning in, down from 7.97m.
Chris Moyles on BBC Radio 1 got 6.32m, down from 6.66m, while Radio 4's 'Today Programme' got 6.12m, down from 6.23m.
On Classic FM, Simon Bates was the most-listened to commercial DJ, with 2.91m listeners, down from 3.05m.
O'Connell's Virgin show attracted 1.25m, up from 1.24m and TalkSport's Alan Brazil got 976,000, down from 995,000.
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